Light emitting apparatus, illuminator, and projector

ABSTRACT

A light emitting apparatus includes a first rod integrator and a second rod integrator supported by a support substrate and a light emitting device disposed between the first rod integrator and the second rod integrator. The light emitting device emits a plurality of light beams to be incident on the first rod integrator and a plurality of light beams to be incident on the second rod integrator. Each of the rod integrators has a light incident surface on which the plurality of light beams are incident, a bent portion that changes the propagating direction of the plurality of incident light beams, and a light exiting surface through which the plurality of light beams mixed with each other exit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation patent application of U.S. application Ser. No.13/084,785 filed Apr. 12, 2011 which claims priority to Japanese PatentApplication No. 2010-159504, filed Jul. 14, 2010 all of which areexpressly incorporated by reference herein in their entireties.

BACKGROUND

1. Technical Field

The present invention relates to a light emitting apparatus, anilluminator, and a projector.

2. Related Art

In a light emitting apparatus including a light emitting device formedof a chip and emitting light beams through both end surfaces of thechip, a mirror is, for example, used in some cases to direct the lightbeams emitted through both end surfaces in the same direction. As anexample of the light emitting apparatus in which a mirror is used tochange the traveling direction of the light beams, JP-A-2009-246407, forexample, discloses a configuration in which two reflection surfacesinclined to the horizontal direction by 45 degrees are provided on asupport member by which a light emitting device that emits light beamsthrough both end surfaces in the horizontal direction is supported sothat the light beams emitted through both end surfaces travel in thesame direction. That is, in the example described in JP-A-2009-246407,the two reflection surfaces provided on the support member function asmirrors for changing the traveling direction of the light beams.

In a light emitting device of this type, each of the end surfaces of thechip has in some cases a plurality of light emitting surfaces in orderto increase the output of the light emitting device. In a light emittingdevice having a plurality of light emitting surfaces, the intensities oflight beams emitted through the light emitting surfaces may differ fromone another in some cases. When the light emitting device in which eachof the end surfaces has a plurality of light emitting surfaces is usedwith the reflection surfaces inclined by 45 degrees to direct the lightbeams emitted through the light emitting surfaces in the same directionas described in JP-A-2009-246407, an area illuminated with the lightbeams disadvantageously has a non-uniform optical intensity distributionbecause the intensities of the light beams emitted through the lightemitting surfaces differ from one another.

SUMMARY

An advantage of some aspects of the invention is to provide a lightemitting apparatus capable of producing a single optical intensitydistribution in an illuminated area.

Another advantage of some aspects of the invention is to provide anilluminator including the light emitting apparatus.

Still another advantage of some aspects of the invention is to provide aprojector including the illuminator.

A light emitting apparatus according to a first aspect of the inventionincludes a support substrate, a first rod integrator and a second rodintegrator supported by the support substrate, and a light emittingdevice supported by the support substrate and disposed between the firstrod integrator and the second rod integrator. The light emitting deviceemits first light and second light to be incident on the first rodintegrator and third light and fourth light to be incident on the secondrod integrator. The first rod integrator has a first light incidentsurface on which the first light and the second light are incident, afirst bent portion that changes the propagating direction of the firstlight and the second light, and a first light exiting surface throughwhich the first light and the second light mixed with each other exittoward a predetermined area. The second rod integrator has a secondlight incident surface on which the third light and the fourth light areincident, a second bent portion that changes the propagating directionof the third light and the fourth light, and a second light exitingsurface through which the third light and the fourth light mixed witheach other exit toward the predetermined area.

According to the light emitting apparatus described above, the first rodintegrator can mix the first light and the second light emitted from thelight emitting device and direct the mixed light toward thepredetermined area, and the second rod integrator can mix the thirdlight and the fourth light emitted from the light emitting device anddirect the mixed light toward the predetermined area. The light emittingapparatus can therefore produce a uniform optical intensity distributionin an illuminated area.

Further, using rod integrators eliminates a need for precise centering,unlike a case where any other optical system for producing a uniformoptical intensity distribution in an illuminated area.

The light emitting apparatus according to the first aspect of theinvention may further include a first cylindrical lens disposed in theoptical paths of the first light and the second light and a secondcylindrical lens disposed in the optical paths of the third light andthe fourth light.

According to the light emitting apparatus described above, since theangle of radiation of the light incident on the first rod integrator canbe reduced, the angle of radiation of the light that exits from thefirst rod integrator can be reduced. Similarly, since the angle ofradiation of the light incident on the second rod integrator can bereduced, the angle of radiation of the light that exits from the secondrod integrator can be reduced.

The light emitting apparatus according to the first aspect of theinvention may further include a first cylindrical lens disposed in theoptical path of the light having exited through the first light exitingsurface and a second cylindrical lens disposed in the optical path ofthe light having exited through the second light exiting surface.

According to the light emitting apparatus described above, the angle ofradiation of the light that exits from the first rod integrator and theangle of radiation of the light that exits from the second rodintegrator can be reduced.

The light emitting apparatus according to the first aspect of theinvention may further include a first polarization converter thatconverts the light having exited through the first light exiting surfaceinto first polarized light and a second polarization converter thatconverts the light having exited through the second light exitingsurface into second polarized light, and the first polarized light andthe second polarized light may be polarized in the same direction.

According to the light emitting apparatus described above, theilluminated area can be illuminated with polarized light.

In the light emitting apparatus according to the first aspect of theinvention, the light emitting device may be a super luminescent diode.

When the light emitting apparatus described above is used as a lightsource in an image projection apparatus, such as a projector, or animage display apparatus, the amount of speckle noise can be reduced.

In the light emitting apparatus according to the first aspect of theinvention, the first light exiting surface and the second light exitingsurface may be oriented in the same direction.

According to the light emitting apparatus described above, the lightthat exits from the first rod integrator and the light that exits fromthe second rod integrator can travel in the same direction.

An illuminator according to a second aspect of the invention includesthe light emitting apparatus according to the first aspect of theinvention, a first lens that causes the light having exited through thefirst light exiting surface of the first rod integrator in the lightemitting apparatus to diverge, a second lens that causes the lighthaving exited through the second light exiting surface of the second rodintegrator in the light emitting apparatus to diverge, a third lens thatsuperimposes the light having exited through the first lens over thelight having exited through the second lens, and a fourth lens thatcauses the light superimposed by the third lens to converge.

The illuminator described above, which includes the light emittingapparatus according to the first aspect of the invention, can produce auniform optical intensity distribution in the illuminated area. Further,since the third lens can superimpose the light fluxes having exitedthrough the two light exiting surfaces over each other, the opticalintensity distribution in the illuminated area can be more uniform.

A projector according to a third aspect of the invention includes theilluminator according to the second aspect of the invention, a lightmodulation apparatus that modulates the light having exited from theilluminator in accordance with image information, and a projectionapparatus that projects an image formed by the light modulationapparatus.

The projector described above, which includes the illuminator accordingto the second aspect of the invention, can project an image having onlya small amount of illuminance unevenness.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a perspective view diagrammatically showing a light emittingapparatus according to an embodiment.

FIG. 2 is a plan view diagrammatically showing the light emittingapparatus according to the embodiment.

FIG. 3 is a cross-section view diagrammatically showing the lightemitting apparatus according to the embodiment.

FIG. 4 is another cross-section view diagrammatically showing the lightemitting apparatus according to the embodiment.

FIG. 5 is a cross-sectional view diagrammatically showing a step ofmanufacturing the light emitting apparatus according to the embodiment.

FIG. 6 is a cross-sectional view diagrammatically showing another stepof manufacturing the light emitting apparatus according to theembodiment.

FIG. 7 is a cross-sectional view diagrammatically showing another stepof manufacturing the light emitting apparatus according to theembodiment.

FIG. 8 is a cross-sectional view diagrammatically showing a lightemitting apparatus according to a first variation of the embodiment.

FIG. 9 is a cross-sectional view diagrammatically showing a lightemitting apparatus according to a second variation of the embodiment.

FIG. 10 is a cross-sectional view diagrammatically showing a lightemitting apparatus according to a third variation of the embodiment.

FIG. 11 is a cross-sectional view diagrammatically showing a lightemitting apparatus according to a fourth variation of the embodiment.

FIG. 12 diagrammatically shows an illuminator according to theembodiment.

FIG. 13 diagrammatically shows a projector according to the embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A preferred embodiment of the invention will be described below withreference to the drawings.

1. Light Emitting Apparatus

A light emitting apparatus 1000 according to the present embodiment willfirst be described with reference to the drawings. FIG. 1 is aperspective view diagrammatically showing the light emitting apparatus1000. FIG. 2 is a plan view diagrammatically showing the light emittingapparatus 1000. FIGS. 3 and 4 are cross-sectional views diagrammaticallyshowing the light emitting apparatus 1000. FIG. 3 is a cross-sectionalview taken along the line in FIG. 2, and FIG. 4 is a cross-sectionalview taken along the line IV-IV in FIG. 2. In FIGS. 1 and 3, a lightemitting device 100 is shown in a simplified form for ease ofillustration.

The light emitting apparatus 1000 includes a support substrate 10, afirst rod integrator 20, a second rod integrator 30, and a lightemitting device 100, as shown in FIGS. 1 to 4. The light emittingapparatus 1000 can further include a sub-mount 150. In the presentembodiment, a description will be made of a case where the lightemitting device 100 is a super luminescent diode (hereinafter alsoreferred to as an “SLD”) made of an InGaAlP-based material (red lightemission). An SLD can prevent laser oscillation because an end surfacereflection resonator is not formed, unlike a semiconductor laser. Theamount of speckle noise can therefore be reduced when the light emittingapparatus 1000 using an SLD is used as a light source in an imageprojection apparatus, such as a projector, or an image displayapparatus.

The support substrate 10 can support the light emitting device 100indirectly via the sub-mount 150. The support substrate 10 mayalternatively support the light emitting device 100 directly without thesub-mount 150. The support substrate 10 can further support the firstrod integrator 20 and the second rod integrator 30. The supportsubstrate 10 can, for example, be a plate-shaped member (box-shapedmember).

The sub-mount 150 is supported by the support substrate 10. Thesub-mount 150 can, for example, be a plate-shaped member. The sub-mount150 can directly support the light emitting device 100.

The thermal conductivity of the support substrate 10 is higher than thatof the sub-mount 150, and the thermal conductivity of the sub-mount 150is higher than that of the light emitting device 100. The thermalconductivity of each of the support substrate 10 and the sub-mount 150is, for example, at least 140 W/mK. The coefficient of thermal expansionof the sub-mount 150 is desirably close to that of the light emittingdevice 100. The reliability of the light emitting device 100 can beimproved by using the sub-mount 150 to reduce the magnitude of stressinduced by the difference in the coefficient of thermal expansionbetween the support substrate 10 and the light emitting device 100. Thesupport substrate 10 is made, for example, of any of Cu, Al, Mo, W, Si,C, Be, Au, a compound thereof (AlN and BeO, for example), and an alloythereof (CuMo, for example). The support substrate 10 may alternativelybe made of a combination of those described above, such as a multilayerstructure formed of a copper (Cu) layer and a molybdenum (Mo) layer. Thesub-mount 150 is made, for example, of a layer made of any of AlN, CuW,SiC, BeO, CuMo, and a multilayer structure formed of copper (Cu) and amolybdenum (Mo) layer (CMC).

A cylindrical through hole 137 is formed through the support substrate10, as shown in FIGS. 2 and 4. A cylindrical terminal 134, the sidesurface of which is covered with an insulating member 136, is providedin the through hole 137. The insulating member 136 is made, for example,of a resin or a ceramic (AlN, for example). The terminal 134 is made,for example, of copper (Cu).

A connection member 132, such as a wire bonding line, connects theterminal 134 to a second electrode 112 of the light emitting device 100.The connection member 132 is so disposed that it does not interfere withthe optical paths of emitted light beams L₁ (L₁₋₁ to L₁₋₄) and L₂ (L₂₋₁to L₂₋₄). A first electrode 114 of the light emitting device 100 isconnected to the sub-mount 150, for example, via plated bumps (notshown). The sub-mount 150 is connected to the support substrate 10. Avoltage can be applied between the first electrode 114 and the secondelectrode 112 by producing a potential difference between the terminal134 and the support substrate 10.

The light emitting device 100 is supported by the support substrate 10via the sub-mount 150. The light emitting device 100 is disposed betweenthe first rod integrator 20 and the second rod integrator 30.

The light emitting device 100 includes a cladding layer (hereinafterreferred to as a “first cladding layer”) 108, an active layer 106 formedthereon, and a cladding layer (hereinafter referred to as a “secondcladding layer”) 104 formed thereon, as shown in FIG. 4. The lightemitting device 100 can further include a substrate 102, a contact layer110, an electrode (hereinafter referred to as a “first electrode”) 114,another electrode (hereinafter referred to as a “second electrode”) 112,and an insulator 116.

The substrate 102 can, for example, be a GaAs substrate of a firstconductive type (n-type, for example).

The second cladding layer 104 is formed under the substrate 102. Thesecond cladding layer 104 can, for example, be an n-type AlGaInP layer.Although not shown, a buffer layer may be formed between the substrate102 and the second cladding layer 104. The buffer layer can, forexample, be an n-type GaAs or InGaP layer.

The active layer 106 is formed under the second cladding layer 104. Theactive layer 106 is disposed in the light emitting device 100, forexample, on the side close to the support substrate 10. The active layer106 is sandwiched between the second cladding layer 104 and the firstcladding layer 108. The active layer 106 has, for example, a multiplequantum well (MQW) structure in which three quantum well structures eachof which is formed of an InGaP well layer and an InGaAlP barrier layerare stacked.

The active layer 106 has, for example, a box-like shape (including acubic shape). The active layer 106 has a first surface 105 facing thefirst rod integrator 20 and a second surface 107 facing the second rodintegrator 30, as shown in FIG. 2. The first surface 105 and the secondsurface 107 face away from each other and parallel to each other in theexample shown in FIG. 2. Among the surfaces of the active layer 106, thefirst surface 105 and the second surface 107 are those that are not incontact with the second cladding layer 104 or the first cladding layer108. It can be said that the first surface 105 and the second surface107 are side surfaces of the active layer 106.

Part of the active layer 106 forms a gain region 160, which serves as acurrent path in the active layer 106. The gain region 160 can producelight, which can be amplified in the gain region 160. The shape of thegain region 160 in a plan view is, for example, a parallelogram. Thegain region 160 is formed of a plurality of gain regions, as shown inFIG. 2. In this way, the output from the light emitting device 100 canbe increased. Each of the gain regions 160 is provided linearly from thefirst surface 105 to the second surface 107 in a direction inclined to anormal P to the first surface 105. The configuration of each of the gainregions 160 suppresses or prevents laser oscillation of the lightproduced therein.

Although not shown, each of the gain regions 160 may alternatively beprovided linearly from the first surface 105 to the second surface 107and in parallel with the normal P to the first surface 105. In thiscase, a resonator is formed and laser light can be produced. That is,the light emitting device 100 may, for example, be a semiconductorlaser.

Each of the gain regions 160 has a light emitting surface 162 providedas part of the first surface 105 and a light emitting surface 164provided as part of the second surface 107. At least two light emittingsurfaces (first light emitting surface 162 a and second light emittingsurface 162 b) are provided as part of the first surface 105, and atleast two light emitting surfaces (third light emitting surface 164 aand fourth light emitting surface 164 b) are provided as part of thesecond surface 107. In the illustrated example, in which four gainregions 160 are provided, four light emitting surfaces 162 and 164 areprovided as part of the first surface 105 and the second surface 107.

The first cladding layer 108 is formed under the active layer 106, asshown in FIG. 4. The first cladding layer 108 can, for example, be anAlGaInP layer of a second conductivity type (p type, for example).

For example, the p-type first cladding layer 108, the active layer 106,to which no impurity has been doped, and the n-type second claddinglayer 104 form a pin diode. Each of the first cladding layer 108 and thesecond cladding layer 104 is a layer having a wider band gap and asmaller refractive index than those of the active layer 106. The activelayer 106 has a function of light amplification. The first claddinglayer 108 and the second cladding layer 104, which sandwich the activelayer 106, have a function of trapping injected carriers (electrons andholes) and light.

The contact layer 110 is formed under the first cladding layer 108. Thecontact layer 110 can be a layer that allows ohmic contact with thefirst electrode 114. The contact layer 110 is made, for example, of asemiconductor material of the second conductivity type. The contactlayer 110 can, for example, be a p-type GaAs layer.

The insulator 116 is formed under the contact layer 110 except theportions below the gain regions 160. That is, the insulator 116 hasopenings located below the gain regions 160, and the openings expose thecorresponding surfaces of the contact layer 110. The insulator 116 can,for example, be a SiN layer, a SiO₂ layer, or a polyimide layer.

The first electrode 114 is formed under the exposed portion of thecontact layer 110 and the insulator 116. The first electrode 114 iselectrically connected to the first cladding layer 108 via the contactlayer 110. The first electrode 114 is one of the electrodes for drivingthe light emitting device 100. The first electrode 114 can, for example,be a Cr layer, a AuZn layer, and a Au layer stacked in this order on thecontact layer 110. The surface where the first electrode 114 is incontact with the contact layer 110 has, for example, the same shape in aplan view as the shape of the corresponding gain region 160. In theillustrated example, the plan shape of the surface in which the firstelectrode 114 is in contact with the contact layer 110 determines thecurrent path between the electrodes 112 and 114 and hence the plan shapeof the corresponding gain region 160.

The second electrode 112 is formed over the entire surface of thesubstrate 102. The second electrode 112 can be in contact with a layerthat allows ohmic contact with the second electrode 112 (the substrate102 in the illustrated example). The second electrode 112 iselectrically connected to the second cladding layer 104 via thesubstrate 102. The second electrode 112 is the other one of theelectrodes for driving the light emitting device 100. The secondelectrode 112 can, for example, be a Cr layer, a AuGe layer, a Ni layer,and a Au layer stacked in this order on the substrate 102. A secondcontact layer (not shown) can further be provided between the secondcladding layer 104 and the substrate 102. In this case, the portion ofthe second contact layer that faces the second cladding layer 104 isexposed, for example, in a dry etching process, and the second electrode112 is provided under the second contact layer. A single-sided electrodestructure can thus be produced. The second contact layer can, forexample, be an n-type GaAs layer.

In the light emitting device 100, when a forward bias voltage at whichthe pin diode is activated is applied between the first electrode 114and the second electrode 112, electrons are recombined with holes in thegain regions 160 of the active layer 106. The recombination leads tolight emission. The produced light triggers stimulated emission in achain reaction, and the light travels through the gain regions 160, andthe intensity of the light is amplified therein. The emitted light beamsL₁ (L₁₋₁ to L₁₋₄) are emitted through the light emitting surfaces 162,and the emitted light beams L₂ (L₂₋₁ to L₂₋₄) are emitted through thelight emitting surfaces 164. The emitted light beams L₁ and L₂ areemitted in a direction inclined to the normal P to the first surface 105by a greater amount than the gain region 160 is inclined to the normalP, for example, due to optical refraction. The emitted light beams L₁and L₂ travel, for example, in the direction parallel to an uppersurface 12 of the support substrate 10 (horizontal direction). Theemitted light beams L₁ and L₂ travel in opposite directions.

The first rod integrator 20 is supported by the support substrate 10.The first rod integrator 20 has a first light incident surface 22, afirst bent portion 23, and a first light exiting surface 24, as shown inFIGS. 1 and 3. The first rod integrator 20 is, for example, acolumn-shaped prism made of glass and having a rectangularcross-sectional shape. The first rod integrator 20 may alternatively bea hollow rod obtained by combining glass plates each having a reflectivecoating in such a way that the reflection surfaces face inward and theresultant structure has a rectangular cross-sectional shape.

On the first light incident surface 22 of the first rod integrator 20are incident at least the emitted light beam (first light beam) L₁₋₁emitted through the first light emitting surface 162 a and the emittedlight beam (second light beam) L₁₋₂ emitted through the second lightemitting surface 162 b. The emitted light beams L₁₋₁ and L₁₋₂ havingbeen incident on the first light incident surface 22 repeatedly undergototal reflection off the inner surface of the first rod integrator 20,and the resultant mixed light flux has a uniform optical intensitydistribution and exits through the first light exiting surface 24. Inthe illustrated example, the emitted light beams L₁₋₁ to L₁₋₄ areincident on the first light incident surface 22. The emitted light beamsL₁₋₁ to L₁₋₄ having been incident on the first light incident surface 22repeatedly undergo total reflection off the inner surface of the firstrod integrator 20, and the resultant mixed light flux has a singleoptical intensity and exits through the first light exiting surface 24.

The first rod integrator 20 has the first bent portion 23, as shown inFIGS. 1 and 3. The first bent portion 23 can change the propagatingdirection of the light in the first rod integrator 20. In theillustrated example, the first rod integrator 20 is bent by 90 degreesat the first bent portion 23. As a result, the direction in which thefirst light incident surface 22 is oriented (the direction of a normalto the first light incident surface 22) forms an angle of 90 degreeswith the direction in which the first light exiting surface 24 isoriented (the direction of a normal to the first light exiting surface24). Therefore, the emitted light beams L₁ emitted through the lightemitting surfaces 162 of the light emitting device 100 and traveling inthe horizontal direction are deflected in the first rod integrator 20and exit as a mixed light flux M₁ that travels in the vertical direction(the direction of a normal to the upper surface 12 of the supportsubstrate 10).

The second rod integrator 30 is supported by the support substrate 10.The second rod integrator 30 has a second light incident surface 32, asecond bent portion 33, and a second light exiting surface 34, as shownin FIG. 3. The second rod integrator 30 is, for example, a column-shapedprism made of glass and having a rectangular cross-sectional shape. Thesecond rod integrator 30 may alternatively be a hollow rod obtained bycombining glass plates each having a reflective coating in such a waythat the reflection surfaces face inward and the resultant structure hasa rectangular cross-sectional shape.

On the second light incident surface 32 of the second rod integrator 30are incident at least the emitted light beam (third light beam) L₂₋₁emitted through the third light emitting surface 164 a and the emittedlight beam (fourth light beam) L₂₋₂ emitted through the fourth lightemitting surface 164 b. The emitted light beams L₂₋₁ and L₂₋₂ havingbeen incident on the second light incident surface 32 repeatedly undergototal reflection off the inner surface of the second rod integrator 30,and the resultant mixed light flux has a uniform optical intensitydistribution and exits through the second light exiting surface 34. Inthe illustrated example, the emitted light beams L₂₋₁ to L₂₋₄ areincident on the second light incident surface 32. The emitted lightbeams L₂₋₁ to L₂₋₄ having been incident on the second light incidentsurface 32 repeatedly undergo total reflection off the inner surface ofthe second rod integrator 30, and the resultant mixed light flux has asingle optical intensity and exits through the second light exitingsurface 34.

The second rod integrator 30 has the second bent portion 33, as shown inFIGS. 1 and 3. The second bent portion 33 can change the propagatingdirection of the light in the second rod integrator 30. In theillustrated example, the second rod integrator 30 is bent by 90 degreesat the second bent portion 33. As a result, the direction in which thesecond light incident surface 32 is oriented (the direction of a normalto the second light incident surface 32) forms an angle of 90 degreeswith the direction in which the second light exiting surface 34 isoriented (the direction of a normal to the second light exiting surface34). Therefore, the emitted light beams L₂ emitted through the lightemitting surfaces 164 of the light emitting device 100 and traveling inthe horizontal direction are deflected in the second rod integrator 30and exit as a mixed light flux M₂ that travels in the verticaldirection.

The mixed light fluxes M₁ and M₂ exit through the first light exitingsurface 24 of the first rod integrator 20 and the second light exitingsurface 34 of the second rod integrator 30, respectively, toward apredetermined area (illuminated area). It is noted that a case wherelight exits through a light exiting surface toward a predetermined areaincludes a case where light exits through a light exiting surfacedirectly toward a predetermined area and a case where light exitsthrough a light exiting surface toward a predetermined area via anoptical system (not shown). The illuminated area can, for example, be alight incident surface of a light valve when the light emittingapparatus 1000 is used as a light source in a projector. The first lightexiting surface 24 of the first rod integrator 20 and the second lightexiting surface 34 of the second rod integrator 30 are oriented in thesame direction (vertically upward with respect to the upper surface 12)in the illustrated example. That is, the mixed light flux M₁ that exitsthrough the first light exiting surface 24 and the mixed light flux M₂that exits through the second light exiting surface 34 travel in thesame direction. The direction in which the light exiting surfaces 24 and34 are oriented is not limited to a specific direction but may be anydirection that allows the exiting light to travel toward an illuminatedarea. For example, the first light exiting surface 24 and the secondlight exiting surface 34 may be oriented in different directions.

The light emitting apparatus 1000 has been described with reference tothe case where the light emitting device 100 is made of an InGaAlP-basedmaterial by way of example, but the light emitting device 100 canalternatively be made of any material that can form a region whereemitted light is amplified. Exemplary useable semiconductor materialsmay include AlGaN-based, InGaN-based, GaAs-based, InGaAs-based,GaInNAs-based, and ZnCdSe-based semiconductor materials.

The light emitting apparatus 1000 has been described with reference tothe case where the light emitting device 100 is a gain guiding type byway of example, but the light emitting device 100 may be a refractiveindex guiding type.

The light emitting apparatus 1000 described above can be used as a lightsource in a projector, a display, an illuminator, a measuringinstrument, and other similar apparatus.

The light emitting apparatus 1000, for example, has the followingfeatures.

According to the light emitting apparatus 1000, the first rod integrator20 mixes the emitted light beams L₁₋₁ and L₁₋₂ emitted from the lightemitting device 100 and allows the mixed light flux to exit, and thesecond rod integrator 30 mixes the emitted light beams L₂₋₁ and L₂₋₂emitted from the light emitting device 100 and allows the mixed lightflux to exit. The light emitting apparatus 1000 can therefore produce auniform optical intensity distribution in an illuminated area.

Further, the configuration using the rod integrators 20 and 30 issuperior to a configuration using any other optical system for producinga uniform optical intensity distribution in an illuminated area becauseno precise centering is necessary, whereby the light emitting apparatuscan be readily manufactured.

In the light emitting apparatus 1000, the first light exiting surface 24of the first rod integrator 20 and the second light exiting surface 34of the second rod integrator 30 are oriented in the same direction. Thetraveling direction of the mixed light flux M₁ can therefore be the sameas that of the mixed light flux M₂. In this way, for example, when thelight emitting apparatus 1000 is used as a light source in an imageprojection apparatus, such as a projector, or an image displayapparatus, it is unnecessary to provide an optical system that causesthe mixed light fluxes M₁ and M₂ to travel in the same direction,whereby the configuration of the optical system in the image projectionapparatus or the image display apparatus can be simplified.

In the light emitting apparatus 1000, the light emitting device 100 canbe an SLD. When the light emitting apparatus 1000 is used as a lightsource in an image projection apparatus, such as a projector, or animage display apparatus, the amount of speckle noise can therefore bereduced.

2. Method for Manufacturing Light Emitting Apparatus

A method for manufacturing the light emitting apparatus 1000 accordingto the present embodiment will next be described with reference to thedrawings. FIGS. 5 to 7 are cross-sectional views diagrammaticallyshowing the steps of manufacturing the light emitting apparatus 1000.

As shown in FIG. 5, the second cladding layer 104, the active layer 106,the first cladding layer 108, and the contact layer 110 are formed inthis order on the substrate 102 in an epitaxial growth process.Exemplary methods for performing the epitaxial growth may include MOCVD(Metal Organic Chemical Vapor Deposition) and MBE (Molecular BeamEpitaxy).

As shown in FIG. 6, the insulator 116 having openings is formed on thecontact layer 110. The insulator 116 is formed, for example, by usingCVD (Chemical Vapor Deposition). The openings are formed by patterningthe insulator, for example, by using photolithography and etchingtechniques so that the corresponding portions of the contact layer 110are exposed.

The first electrode 114 is then formed on the exposed contact layer 110and the insulator 116. The second electrode 112 is then formed on thelower surface of the substrate 102. The first electrode 114 and thesecond electrode 112 are formed, for example, by using vacuumdeposition. The first electrode 114 and the second electrode 112 are notnecessarily formed in a particularly specific order. The light emittingdevice 100 can be formed by carrying out the steps described above.

As shown in FIG. 7, the through hole 137 is formed through the supportsubstrate 10 by using a known method. The insulating member 136 is thenformed to cover the inner side surface of the through hole 137 but notto entirely block the through hole 137. The insulating member 136 isdeposited, for example, in a CVD process. The rod-shaped terminal 134 isthen inserted into a space inside the insulating member 136.Alternatively, the insulating member 136 may be formed around therod-shaped terminal 134, and the terminal 134 with the insulating member136 therearound may then be inserted into the through hole 137.

As shown in FIG. 4, the light emitting device 100 is first mounted onthe sub-mount 150, and the sub-mount 150 on which the light emittingdevice 100 has been mounted is then mounted on the support substrate 10.The light emitting device 100 is so mounted that the active layer 106 isdisposed on the side close to the support substrate 10 (junction-downmounting). That is, the light emitting device 100 can be mounted in aflip-chip manner.

The terminal 134 is then connected to the second electrode 112 of thelight emitting device 100 via the connecting member 132. The presentstep is carried out, for example, in a wire bonding process.

As shown in FIGS. 1 to 3, the rod integrators 20 and 30 are disposed onthe support substrate 10. The rod integrators 20 and 30 are so disposedthat the light emitting device 100 is located between the rodintegrators 20 and 30. In the process in which the rod integrators 20and 30 are disposed, the optical axes thereof are adjusted with respectto the emitted light beams L₁ and L₂. A rod integrator does not requireprecise centering, unlike other optical systems that produce a uniformoptical intensity distribution in an illuminated area. Using the rodintegrators therefore allows the manufacturing steps to be simplified.The rod integrators 20 and 30 are fixed to the support substrate 10, forexample, with an adhesive.

The light emitting apparatus 1000 can be manufactured by carrying outthe steps described above.

3. Variations of Light Emitting Apparatus

Light emitting apparatus according to variations of the presentembodiment will next be described with reference to the drawings. In thefollowing light emitting apparatus according to the variations of thepresent embodiment, members having the same functions as those of thecomponents of the light emitting apparatus 1000 according to the presentembodiment have the same reference characters, and no detaileddescription of those members will be made.

3-1. A description will first be made of a light emitting apparatus 2000according to a first variation of the present embodiment. FIG. 8 is across-sectional view diagrammatically showing the light emittingapparatus 2000. In FIG. 8, the light emitting device 100 is shown in asimplified form for ease of illustration.

The light emitting apparatus 2000 includes a first cylindrical lens 210and a second cylindrical lens 220, as shown in FIG. 8. The firstcylindrical lens 210 is disposed somewhere in the optical paths of theemitted light beams L₁ and between the light emitting device 100 and thefirst rod integrator 20. The second cylindrical lens 220 is disposedsomewhere in the optical paths of the emitted light beams L₂ and betweenthe light emitting device 100 and the second rod integrator 30. In theillustrated example, the cylindrical lenses 210 and 220 are so disposedthat they are in contact with the light incident surfaces 22 and 32 ofthe rod integrators 20 and 30.

In general, an SLD, a semiconductor laser, or any other similar lightemitting device emits light having a large angle of radiation. Inparticular, light emitted from an SLD, a semiconductor laser, or anyother similar light emitting device has a larger angle of radiation inthe thickness direction of the active layer than the angle of radiationof the emitted light in the in-plane direction. In the illustratedexample, the thickness direction of the active layer 106 is thedirection of a normal to the upper surface 12 of the support substrate10, and the in-plane direction of the active layer 106 is the in-planedirection of the upper surface 12 of the support substrate 10 (see FIG.4). In the light emitting apparatus 2000, the first cylindrical lens 210disposed in the optical paths of the emitted light beams L₁ and thesecond cylindrical lens 220 disposed in the optical paths of the emittedlight beams L₂ can reduce the angles of radiation of the emitted lightbeams L₁ and L₂ in the thickness direction of the active layer 106. Theangles of radiation of the mixed light fluxes M₁ and M₂ that exitthrough the rod integrators 20 and 30 can therefore be reduced.

3-2. A light emitting apparatus 3000 according to a second variation ofthe present embodiment will next be described.

FIG. 9 is a cross-sectional view diagrammatically showing the lightemitting apparatus 3000. In FIG. 9, the light emitting device 100 isshown in a simplified form for ease of illustration. In the followinglight emitting apparatus according to the second variation, membershaving the same functions as those of the components of the lightemitting apparatus 2000 have the same reference characters, and nodetailed description of those members will be made.

The light emitting apparatus 3000 includes a first cylindrical lens 210and a second cylindrical lens 220, as shown in FIG. 9. The firstcylindrical lens 210 is disposed somewhere in the optical path of themixed light flux M₁ having exited through the first light exitingsurface 24 of the first rod integrator 20. The second cylindrical lens220 is disposed somewhere in the optical path of the mixed light flux M₂having exited through the second light exiting surface 34 of the secondrod integrator 30. In the illustrated example, the cylindrical lenses210 and 220 are so disposed that they are in contact with the lightexiting surfaces 24 and 34 of the rod integrators 20 and 30.

In the light emitting apparatus 3000, the first cylindrical lens 210disposed in the optical path of the mixed light flux M₁ and the secondcylindrical lens 220 disposed in the optical path of the mixed lightflux M₂ can reduce the angles of radiation of the mixed light fluxes M₁and M₂ having exited through the rod integrators 20 and 30. Further, inthe light emitting apparatus 3000, since the light fluxes having passedthrough the rod integrators 20 and 30 are incident on the cylindricallenses 210 and 220, the angles of radiation of the mixed light fluxes M₁and M₂ can be reduced without reduction in the angle of incidence of thelight incident on the rod integrators 20 and 30. Therefore, in the lightemitting apparatus 3000, the rod integrators 20 and 30 can produce auniform optical intensity distribution more efficiently than in thelight emitting apparatus 2000.

3-3. A light emitting apparatus 4000 according to a third variation ofthe present embodiment will next be described. FIG. 10 is across-sectional view diagrammatically showing the light emittingapparatus 4000. In FIG. 10, the light emitting device 100 is shown in asimplified form for ease of illustration.

The light emitting apparatus 4000 includes a first polarizationconverter 410 and a second polarization converter 420, as shown in FIG.10. The first polarization converter 410 is disposed somewhere in theoptical path of the mixed light flux M₁ having exited through the firstlight exiting surface 24 of the first rod integrator 20. The mixed lightflux M₁ is incident on the first polarization converter 410. The secondpolarization converter 420 is disposed somewhere in the optical path ofthe mixed light flux M₂ having exited through the second light exitingsurface 34 of the second rod integrator 30. The mixed light flux M₂ isincident on the second polarization converter 420. In the illustratedexample, the polarization converters 410 and 420 are so disposed thatthey are in contact with the light exiting surfaces 24 and 34 of the rodintegrators 20 and 30.

The first polarization converter 410 includes a first polarizing beamsplitter 412, a first mirror 414, and a first half-wave plate 416. Thefirst polarizing beam splitter 412 can transmit a P-polarized componentof the mixed light flux M₁ and reflect an S-polarized component thereof.The first mirror 414 can reflect again the S-polarized component of themixed light flux M₁ reflected off the first polarizing beam splitter 412and direct the reflected S-polarized component to the first half-waveplate 416. The first half-wave plate 416 can convert the S-polarizedcomponent of the mixed light flux M₁ into the P-polarized component. Thefirst polarization converter 410, which includes the first polarizingbeam splitter 412, the first mirror 414, and the first half-wave plate416, converts the S-polarized component of the mixed light flux M₁ intothe P-polarized component, for example, allows the mixed light flux M₁to be formed of only the P-polarized component. The first polarizationconverter 410 can thus convert the mixed light flux M₁ into a polarizedlight flux P₁.

The second polarization converter 420 includes a second polarizing beamsplitter 422, a second mirror 424, and a second half-wave plate 426. Thesecond polarizing beam splitter 422 can transmit the P-polarizedcomponent of the mixed light flux M₂ and reflect the S-polarizedcomponent thereof. The second mirror 424 can reflect again theS-polarized component of the mixed light flux M₂ reflected off thesecond polarizing beam splitter 422 and direct the reflected S-polarizedcomponent to the second half-wave plate 426. The second half-wave plate426 can convert the S-polarized component of the mixed light flux M₂into the P-polarized component. The second polarization converter 420,which includes the second polarizing beam splitter 422, the secondmirror 424, and the second half-wave plate 426, converts the S-polarizedcomponent of the mixed light flux M₂ into the P-polarized component, forexample, allows the mixed light M₂ to be formed of only the P-polarizedcomponent. The second polarization converter 420 can thus convert themixed light flux M₂ into a polarized light flux P₂.

In the light emitting apparatus 4000, the first polarization converter410 can convert the mixed light flux M₁ into the polarized light fluxP₁, and the second polarization converter 420 can convert the mixedlight flux M₂ into the polarized light flux P₂. The polarizationconverters 410 and 420 can further align the polarization directions ofthe polarized light flux P₁ and the polarized light flux P₂ with eachother. Therefore, in the light emitting apparatus 4000, an illuminatedarea can be illuminated with polarized light.

The above description has been made of the case where the polarizationconverters 410 and 420 convert the S-polarized component of the mixedlight fluxes M₁ and M₂ into the P-polarized component. The polarizationconverters 410 and 420 may alternatively convert the P-polarizedcomponent of the mixed light fluxes M₁ and M₂ into the S-polarizedcomponent.

3-4. A light emitting apparatus 5000 according to a fourth variation ofthe present embodiment will next be described. FIG. 11 is across-sectional view diagrammatically showing the light emittingapparatus 5000.

In the example of the light emitting apparatus 1000, the active layer106 is disposed on the side close to the support substrate 10 in thelight emitting device 100, as shown in FIG. 4. In contrast, in the lightemitting apparatus 5000, the active layer 106 is disposed on the sideaway from the support substrate 10 in the light emitting device 100, asshown in FIG. 11. In the light emitting apparatus 5000, the substrate102 is disposed between the active layer 106 and the support substrate10. The second electrode 112 is connected to the sub-mount 150, forexample, via connecting members (not shown). The first electrode 114 isconnected to the terminal 134, for example, via the connecting member132.

According to the light emitting apparatus 5000, since the substrate 102is disposed between the active layer 106 and the support substrate 10,the active layer 106 is further set apart from the support substrate 10by at least a distance corresponding to the substrate 102, as comparedwith the light emitting apparatus 1000. It is therefore possible toprevent the amount of light emitted from the gain regions 160 fromdecreasing before incident on the rod integrators. For example, when thelight emitted from each of the gain regions 160 has a large angle ofradiation, part of the emitted light is blocked by the support substrate10 and the amount of light incident on the rod integrators decreases insome cases. The problem will not occur in the light emitting apparatus5000.

In the light emitting apparatus of the present embodiment as well as inthe present variation, the rod integrators 20 and 30 are desirablydisposed in positions close to the light emitting surfaces 162 and 164of the light emitting device 100. The rod integrators are more desirablyin contact with the light emitting surfaces of the light emittingdevice. In this way, the light emitting device is coupled with the rodintegrators more efficiently, whereby the light emitting apparatus canuse light more efficiently. Further, a reflection film may be formed onthe support substrate between the light emitting device 100 and the rodintegrators 20, 30 so that light blocked by the substrate is reflectedoff the reflection film toward the rod integrators.

4. Illuminator

An illuminator according to the present embodiment will next bedescribed with reference to the drawings. FIG. 12 diagrammatically showsan illuminator 6000 according to the present embodiment. In thefollowing illuminator according to the present embodiment, membershaving the same functions as those of the components of the lightemitting apparatus 1000 according to the present embodiment have thesame reference characters, and no detailed description of those memberswill be made.

The illuminator 6000 includes the light emitting apparatus 1000, a firstlens 610 for causing the light having exited through the first lightexiting surface 24 of the first rod integrator 20 to diverge, a secondlens 612 for causing the light having exited through the second lightexiting surface 34 of the second rod integrator 30 to diverge, a thirdlens 620 for causing the light having exited through the first lens 610to be superimposed over the light having exited through the second lens612, and a fourth lens 630 for causing the light superimposed by thethird lens 620 to converge.

The illuminator 6000 includes a light emitting apparatus according to anembodiment of the invention. The following description will be made of acase where the illuminator 6000 includes the light emitting apparatus1000 as a light emitting apparatus according to an embodiment of theinvention.

The first lens 610 causes the light having exited through the firstlight exiting surface 24 of the first rod integrator 20 to diverge.Specifically, the first lens 610 causes the light having exited throughthe first light exiting surface 24 to converge first and then diverge.The first lens 610 can cause the light having exited through the firstlight exiting surface 24 to diverge to a point where the area that theilluminator 6000 can illuminate is enlarged to a desired size (the sizeof a light incident surface of a light valve, for example). The firstlens 610 is, for example, a condenser lens.

In the illustrated example, the first lens 610 is a single lens but maybe a combination of a plurality of lenses. The same applies to thelenses 612, 620, and 630, which will be described later.

The second lens 612 causes the light having exited through the secondlight exiting surface 34 of the second rod integrator 30 to diverge.Specifically, the second lens 612 causes the light having exited throughthe second light exiting surface 34 to converge first and then diverge.The second lens 612 can cause the light having exited through the secondlight exiting surface 34 to diverge to a point where the area that theilluminator 6000 can illuminate is enlarged to a desired size (the sizeof a light incident surface of a light valve, for example). The secondlens 612 is, for example, a condenser lens.

The third lens 620 causes the light having exited through the first lens610 to be superimposed over the light having exited through the secondlens 612. The light having exited through the first lens 610 issuperimposed over the light having exited through the second lens 612 bythe third lens 620, and the resultant light is incident on the fourthlens 630.

The fourth lens 630 causes the light superimposed by the third lens 620to converge. In the illustrated example, the fourth lens 630 causes thelight superimposed by the third lens 620 to converge in an illuminatedarea (a light incident surface of a light valve, for example) 640. Thatis, the light superimposed by the third lens 620 converges after passingthrough the fourth lens 630 and illuminates the illuminated area 640.

The illuminator 6000, which includes the light emitting apparatus 1000,can produce a uniform optical intensity distribution in the illuminatedarea 640.

In the illuminator 6000, since the third lens 620 can superimpose thelight fluxes having exited through the two light exiting surfaces 24 and34 over each other, the optical intensity distribution in theilluminated area 640 can be more uniform. For example, when theintensity of the light having exited through the first light exitingsurface 24 differs from that of the light having exited through thesecond light exiting surface 34, and the illuminated area 640 isilluminated with the light having exited through the first light exitingsurface 24 and the light having exited through the second light exitingsurface 34 that have not undergone any superposition, the opticalintensity distribution in the illuminated area 640 reflects thedifference in intensity. The problem will not occur in the illuminator6000.

5. Projector

A projector 7000 according to the present embodiment will be nextdescribed with reference to the drawings. FIG. 13 diagrammatically showsthe projector 7000. In FIG. 13, an enclosure that is part of theprojector 7000 is omitted for ease of illustration.

In the projector 7000, a red light source (illuminator) 6000R that emitsred light, a green light source (illuminator) 6000G that emits greenlight, and a blue light source (illuminator) 6000B that emits blue lightare illuminators according to an embodiment of the invention(illuminator 6000, for example).

The projector 7000 includes transmissive liquid crystal light valves(light modulation apparatus) 704R, 704G, and 704B that modulate lightbeams emitted from the light sources 6000R, 6000G, and 6000B inaccordance with image information and a projection lens (projectionapparatus) 708 that enlarges images formed by the liquid crystal lightvalves 704R, 704G, and 704B and projects the enlarged images on a screen(displayed surface) 710. The projector 7000 can further include a crossdichroic prism (light combiner) 706 that combines light fluxes outputtedfrom the liquid crystal light valves 704R, 704G, and 704B and guides thecombined light to the projection lens 708.

The three color light fluxes modulated by the liquid crystal lightvalves 704R, 704G, and 704B are incident on the cross dichroic prism706. The prism is formed by bonding four rectangular prisms and thus hasinternal surfaces that intersect each other in an X-like shape. One ofthe internal surfaces has a dielectric multilayer film that reflects redlight, and the other internal surface has a dielectric multilayer filmthat reflects blue light. The dielectric multilayer films combine thethree color light fluxes to form light representing a color image. Theprojection lens 708, which is a projection system, projects the combinedlight on the screen 710 and displays an enlarged image.

As described above, the projector 7000 can use the illuminator 6000,which can produce a uniform optical intensity distribution in anilluminated area, as a light source. The projector 7000 can thereforeproject an image having only a small amount of illuminance unevenness.

In the example described above, transmissive liquid crystal light valvesare used as the light modulation apparatus. Alternatively, any lightvalve that does not use a liquid crystal material or a reflective lightvalve may be used. Examples of the alternative light valve may include areflective liquid crystal light valve and a digital micromirror device.The configuration of the projection system is changed as appropriate inaccordance with the type of a light valve to be used.

The embodiment and the variations described above have been presented byway of example, and the invention is not limited thereto. For example,any of the embodiment and the variations can be combined as appropriate.

The embodiment of the invention has been described in detail, and theskilled in the art will readily understand that many changes can be madeto the extent that they do not substantially depart from the novelfeatures and advantageous effects of the invention. All such variationsare therefore intended to fall within the scope of the invention.

What is claimed is:
 1. A light emitting apparatus comprising: a firstrod integrator and a second rod integrator; and a light emitting devicedisposed between the first rod integrator and the second rod integrator,wherein the light emitting device emits first light and second light tobe incident on the first rod integrator, and third light and fourthlight to be incident on the second rod integrator, the first rodintegrator has: a first light incident surface on which the first lightand the second light are incident, a first bent portion that changes thepropagating direction of the first light and the second light, and afirst light exiting surface through which the first light and the secondlight exit toward a predetermined area, and the second rod integratorhas: a second light incident surface on which the third light and thefourth light are incident, a second bent portion that changes thepropagating direction of the third light and the fourth light, and asecond light exiting surface through which the third light and thefourth light exit toward the predetermined area.
 2. The light emittingapparatus according to claim 1, further comprising: a first cylindricallens disposed in the optical paths of the first light and the secondlight; and a second cylindrical lens disposed in the optical paths ofthe third light and the fourth light.
 3. The light emitting apparatusaccording to claim 1, further comprising: a first cylindrical lensdisposed in the optical path of the light having exited through thefirst light exiting surface; and a second cylindrical lens disposed inthe optical path of the light having exited through the second lightexiting surface.
 4. The light emitting apparatus according to claim 1,further comprising: a first polarization converter that converts thelight having exited through the first light exiting surface into firstpolarized light; and a second polarization converter that converts thelight having exited through the second light exiting surface into secondpolarized light, wherein the first polarized light and the secondpolarized light are polarized in the same direction.
 5. The lightemitting apparatus according to claim 1, wherein the light emittingdevice is a super luminescent diode.
 6. The light emitting apparatusaccording to claim 1, wherein the first light exiting surface and thesecond light exiting surface are oriented in the same direction.
 7. Anilluminator comprising: the light emitting apparatus according to claim1; a first lens that causes the light having exited through the firstlight exiting surface of the first rod integrator in the light emittingapparatus to diverge; a second lens that causes the light having exitedthrough the second light exiting surface of the second rod integrator inthe light emitting apparatus to diverge; a third lens that superimposesthe light having exited through the first lens over the light havingexited through the second lens; and a fourth lens that causes the lightsuperimposed by the third lens to converge.
 8. A projector comprising:the illuminator according to claim 7; a light modulation apparatus thatmodulates the light having exited from the illuminator in accordancewith image information; and a projection apparatus that projects animage formed by the light modulation apparatus.